When Were the American Continents First Colonized?

Four Theories of the Original Colonization of the Americas

Coast of British Columbia near Zeballos
Coast of British Columbia near Zeballos. Alexis Harrison

The original population of America, that is to say, the date and pathway of the first human occupants of the American continents is still perhaps one of the most highly debated topics in archaeology today. The main disputes are: the pathway(s) into the Americas and the timing and number of the migrations of people that arrived in both continents prior to the arrival of the Europeans.

Pathways into America: Four Theories

There are no less than four major routes that scholars have seriously put forth over the past hundred years or so; each has its proponents and detractors.

One paper published by Perego et al. in January of 2009 suggested that Native Americans arrived in several waves into the Americas using two of these entryways: the Ice Free Corridor and migration along the Pacific Coast. The Ice-Free Corridor, however, may not have been opened at the time of the first colonization; and the waves may not have come from Siberia at all.

Timing of the Arrival(s)

The theory with the most proponents these days is that humans first arrived from the now-sunken landmass known as Beringia (or the Bering Land Bridge) and moved down into the continents along the coastlines, (the Pacific Coast Migration model). That theory became more likely as the evidence for people in the Americas earlier than the traditionally accepted first colonists called Clovis hunters has become more widely accepted.

This earliest culture in the Americas is known as pre-Clovis. Although so far little is known about when pre-Clovis people arrived in the Americas (firm dates are no earlier than, say, 16,000 years ago), it is clear that they practiced a broad-based hunting-fishing-gathering lifestyle.

One reason there is still so much unsettled discussion has in part to do with the timing and character of the Last Glacial Maximum (LGM).

During the LGM, the most likely routes into North America were blocked by glacial ice between at least 18,000 and 24,000 calendar years ago (cal BP), and perhaps as long ago as 30,000 cal BP, and yet there are a handful of archaeological sites that appear to have dates older than 18,000.

Genetics and the New World Entrada

Continuing scholarly research has also attempted to understand the genetic, archaeological and linguistic diversity and similarities of Native American populations. The possibility that multiple waves of people arrived from Asia has been researched for decades. DNA and linguistic analyses have been brought to the discussion, but neither yet provides an unequivocal answer. A paper by Perego et al. (2010) reported evidence for at least 15 maternal founding lineages and hinted that there may have been quite a few more.

A comprehensive study published in Nature in 2012 (Reich et al.) assembled DNA data from 52 Native American and 17 Siberian groups and identified at least three streams of Asian gene flow. Reich et al. confirm that the majority of Native American populations did originate from the first push, a fairly homogenous group that left Beringia more than 15,000 years ago.

Two later migrations of people still are mostly from the first group. One migration result is that speakers of Eskimo-Aleut languages share about half their ancestry from a second migration, and Chipewyan Na-Dene speakers from Canadz share about 1/10th of their ancestry from a third Siberian stream.

The Beringian Incubation Model

The homogeneity of that first push, however, supports the Beringian Standstill Hypothesis (or the Beringian Incubation Model), which argues that Beringia was an open habitable tundral plain but isolated from Siberia and the Americas by glaciers during OIS2, between 25,000 and 18,500 cal BP and occupied by the  ancestors of the first American colonists for perhaps as long as 10,000-20,000 years.

If there were multiple waves, goes the theory, they originated from that single population, not different groups from Asia proper.

Important Sites of the Colonization of America

American Pre-Clovis Sites

Other Important American Sites:
Kennewick Man Washington, Murray Springs Arizona, Daisy Cave California, Charlie Lake Cave British Columbia

Russia: Yana RHS, Dyuktai Cave, Ushki Lakes, Ust-Mil, Mal'ta


Additional sources are listed on the pages dedicated to the various models.

Gonzalez, S. 2007 Archaeological Records: Global Expansion 300,000-8000 years ago, Americas. pp. 129-135 in Encyclopedia of Quaternary Science, ed. Scott A. Elias. Elsevier: London. Just found this good summary of the issues.

Hoffecker JF, Elias SA, and O'Rourke DH. 2014. Out of Beringia? Science 343:979-980. doi: 10.1126/science.1250768

Perego, Ugo A., et al. 2009 Distinctive Paleo-Indian Migration Routes from Beringia Marked by Two Rare mtDNA Haplogroups. Current Biology 191-8.

Perego UA, Angerhofer N, Pala M, Olivieri A, Lancioni H, Kashani BH, Carossa V, Ekins JE, Gómez-Carballa A, Huber G et al. 2010. The initial peopling of the Americas: A growing number of founding mitochondrial genomes from Beringia. Genome Research (advance publication, currently free to download)

Reich D, Patterson N, Campbell D, Tandon A, Mazieres S, Ray N, Parra MV, Rojas W, Duque C, Mesa N et al. 2012. Reconstructing Native American population history. Nature 488(7411):370-374. doi: 10.1038/nature11258

A Preclovis vs Clovis bibliography has been built for this project.